Transverse flux induction heating apparatus



Aug. 31, 1948. G. E. STOLTZ 2,448,062

7 TRANSVERSE FLUX INDUCTION HEATING APPARATUS Filed Sept. 9, 1944 'q .50 /6 5 'q 32 2 "G 3 w 0 u a 5- u SE 3- qgu . um; 42 3 p 3 1 riecr i k ifil ii 4 WITNESSES: INVENTOR gflW G/erm E 570/72. 4 BY lZ h a zzw wef ATTORN EY Patented Aug. 31, 1948 UNITED- STATES PAT-Eur c t-Pics TRAN SVERSE FLUX INDUC'IIGN HEATING- APPARATUS Glenn astltz, Pittsburgh Passag s mi w stinghouse Electric Corporatio'm l last Pittsburgh, Pa, a corporation of Pennsylvania Application September 9, 1944, Serial No. 553,363

3 Claims. (01. 219-13) This invention relates generally to inductive heating of separatedlongitudinal parts of moving material, by longitudinal meaning alongthe direction in which the material moves; but more specifically relates to flowing tin which has been electroplated only along the edges of metal strip or'the like. 7 I

It is an objector rnyinvention to provide an induction heating system for heating material having one or more lengthwise stripes which are less than the width of the material itself.

In accordance with my invention, I provide an induction heating equipment arranged to induce heat that is concentrated in the part of the material for the coating, without necessarily inducing heat in the uncoated part of the material, thereby conserving power. Preferably, the induction heating means is of a type providing a transverse magnetic flux, along the lines of the systems disclosed in the'ap'plications of R. M. Baker, Serial No. 521,229, filed February 5, 1944, andSerial No. 553,381, filed September 9, 1944. Such system are especially suitable for heating elongated and thin metal materials, such as strips, sheets, plates, and the like, 7 v

A feature ofmy invention resides in centering the material passing through the heat-inducing magnetic field, so'that the proper parts of the material will be heated and so that any tendency of the material to whip or to be attracted to a flux-producing element is resisted.

Other objects, features, and innovations of my invention will be discernible from the following description thereof, which is to be taken in conjunction with the accompanying schematic drawmg.

In the drawing, which is not toscale K Figure 1 is an"'elevational view of apparatus embodying my invention;

Fig. 2 is a plan View of the apparatus; and

Fig. 3 is a vertical sectional view thereoflsubstanti ally on the line III -III of Fig. 1, with the coating thicknessexaggerated, I

For illustrating my invention, I have chosen a flexible piece of thin iron sheetZ which had been previously centrally lacquered and then passed through an electroplating bath, so that'its bare border porti-ons'along the edges of the sheet receive a matte coating 3 of tin plate. By the term border-portion, I includein its scop the lateral parts 4 of the sheet, underneath the coating 3, by lateral meaning in the direction of the width of the sheet. I I I In accordance with the purposes of my inven tion, the sheet is passed into an" apparatus which raises the temperature of the. metal along-its tinned border-portions 4 to a value 'aboutthe melting point of tin, so that the tin coating flows. Upon cooling, such a coating solidifies ,into Ia bright and more corrosion res'istant surface, such as more particularly described in the copending application of R. M. Baker and myself, Serial No, 464,040, filed October'31, 1942, now abandoned. v

A preferred form of apparatus for carrying out my invention comprises induction heating means of limited lateral extent, means for passing the tinned border-portionsof the sheet, through the heatingmeans, and means for causing the sheet to pass in a certain predetermined relation with respect to the heating means as it passes thereby.

Referring more particularly to the, drawing, the sheet 2 is properly guided by, any suitable guide means, into the entrance end of a pair of endless belts which, are indicated in, their entirety by reference numerals 6 and 8, respectively; the sheet being received between opposite -parallel aligned stretches or runs I 0 and [2 of the belts 6 and 8, respectively. Th belts are driven in any suitable manner, sothat the runs Ill and l2,move at thesame linear speed, Either a single belt or both belts may be positively driven.

The belts 6 and 8 are of heat-resistant material, ,such as asbestos or woven glass, and are of a width which is less thanthe distance between the coatings 3 of the sheet 2, so as not to scratch or otherwise mar the thin tin coatings. A plurality of, spaced guiderollers l6, between the runs bf the belt 6, and a plurality of spaced guide rollers l8,v between the runs of the,.be lt 8, guide the sheet to and from a field producing induction heating means which is indicated in its entirety by the reference numeral v20. If. desired, the groups of. rollers I6 .or. J8, vor both,.may be driving rollers which press the sheet 2. between the belt runs l0 and I2 and cause-it to move through the heating means, in addition to positioning the sheet. The induction-heating means 28 may be of any type which will inductively heat the particular coating or the parts of the material having the coating thereon, In this particular instance, the induction heating meanslfl is of the electro-magnetic type which providescon- 'centrated magnetic fields of energy through'the use of iron cores. I,

In order to economizeon the induction heatingmeans and to limit, the heating tothe portion of thesheet having, the tin coating thereon, the heating means comprises apair-ofl laminated ore-or'field structure's 22 and 24on one side of the sheet 2 passing thereby, and similar spaced core-or field-structures 26 and 28 on the other side of the sheet, the field-structures being laterally spaced from the end-edges of the endless belts B and 8. Each field-structure comprises a plurality of comb-shaped, stacked laminations having teeth 30 surrounded by coils 32. The coils are so connected and energized by alternating current as to create a rapidly reversing magnetic flux which, at any instant, passes from a tooth of one core-structure to the directly opposite tooth of the core-structure on the other side of the sheet, for example, between the corestructures 22 and 26, thereby providing what is known as transverse flux, because the flux passes transversely through the sheet and across the work-passage between the core-structures, through which the sheet 2 passes. The workpassage referred to may be considered that space provided in the apparatus for accommodating the sheet 2 in the region of the field-structures; this work-passage being indicated by the reference numeral 34.

The work-passage 34 comprises the space for the field between the opposite core-structures 22 and 26, the space for the field between the opposite core-structures 24 and 2B, and the lateral space between and merging with such energypermeated spaces. In order to further guide the sheet through the work-passage 34 and fix its position relative to the core-structures, guide rollers 38 are provided between the core-structures 22 and 24; and cooperating guide rollers 40 are provided between the core-structures 2E and 28.

Each guide roller 38 is supported in a pair of guide bearings 42 in opposite brackets 44 which are removably and adjustably fastened to the core-structures 22 and 24; and similarly each guide roller 40 is supported in guide bearings 46 in opposite brackets 48 which are removably and adiustably fastened to the core-structures 26 and 28.

In operatiomthe sheet 2 is, of course, placed in the entrance end of the endless belts 6 and 8. Several pairs of adjustably spaced roller guide shafts 50 may be provided for assuring a proper centering of the sheet, as it is conveyed to the heating means 2!]. The sheet is maintained centered by aligned pairs of the rollers l6 and I8 and of the rollers 38 and 40, any evenness in the sheet being accommodated by the flexibility of the material of the belts, although these rollers may be spring-pressed in any commonly known manner. In passing between the energized corestructures, on opposite sides of the work-passage 34, electric currents are induced in the border-portions of the sheet, which heat such border-portions to a temperature depending upon the physical properties and speed of the coated sheet, the strength of the magnetic field, the frequency of the alternating current passing through the magnetizing coils 32, and the longitudinal length of the core-structures.

The core-structures 22 and 24 on one side of the work-passage and the core-structures 26 and 28 on the other side of the work-passage are each of such width and are each so disposed that the magnetic field provided by them is concentrated substantially in the stripes on the sheet provided by the coatings to be flowed. In order to accommodate different widths of coatings, the corestructures can be made substantially as wide as the widest coating that is expected to be passed through the apparatus. In the embodiment shown, the heat-producing magnetic field will be concentrated in and contiguous to the spaces between opposite cooperating pairs of core-structures; but as is apparent to those skilled in magnetisrn, stray flux-lines of no significant heating power, may spread out further. To control the heating across the width of the tinned surface, adjustable copper shields may be used to reduce the temperature of those sections that tend to overheat, particularly along the edges of the sheet, as described in th aforesaid Baker application, Serial No. 553,381.

Although the apparatus has been described in connection with the flowing of a tin coating along the edges of a piece of iron sheet, it is obvious that the apparatus can be used to treat other coatings and other material, including continuous elongated strip, sheet, and coilable material.

While I have described my invention in a simple symbolic form, it is obvious that many modifications and equivalents will suggest themselves from the teachings of my invention. For example, it is within the scope of my invention to make the apparatus described more universal by mounting the core-structures, the endless belts and the various rollers so that they can be adjusted to accommodate different thickness of materials to be heat-treated; and to use a field of energy other than transverse magnetic flux. Also the inductive heating may be accomplished by induction structure or structures either only above or below the strip or sheet to be heated.

I claim as my invention:

1. Induction heating apparatus provided with a work-passage, said induction heating apparatus comprising, in combination, a plurality of cooperating pairs of electrically-energizable field-establishing means, each pair comprising spaced facing cores for producing a narrow concentrated heat-inducing magnetic field extending across the depth of the work-passage, each core of one pair of field-establishing means also being laterally spaced from a core on the same side of the work-passage which is a part of another pair of said field-establishing means, means for moving material so that separate parts of the material longitudinally pass through said magnetic fields, the last said means comprising a plurality of endless non-magnetic belts having opposite substantially parallel runs for receiving material therebetween, the said runs being outside of said concentrated magnetic fields, and roller means laterally between the cores on the same side of the work-passage, said roller means bearing on the relatively outer sides of said opposite runs, and being so arranged as to maintain a space between said opposite runs which is narrower than the corresponding space between the cores of each of said cooperating pairs of field-establishing means.

2. Induction heating apparatus provided with a work-passage, said induction heating apparatus comprising, in combination, a plurality of cooperating pairs of electrically-energizable fieldestablishing means, each pair comprising spaced facing cores for producing a narrow concentrated heat-inducing magnetic field extending across the depth of the work-passage, each core of one pair of field-establishing means also being laterally spaced from a core on the same side of the work-passage which is a part of another pair of said field-establishing means, means for moving material so that separate parts of the material longitudinally pass through said magnetic fields, the last said means comprising a plurality of endless belts having opposite substantially parallel runs for receiving material therebetween, the said runs being outside of said concentrated magnetic fields, and roller means laterally between the cores on the same side of the work-passage, said roller means bearing on the relativly outer sides of said opposite runs.

3. Induction heating apparatus provided with a work-passage, said induction heating apparatus comprising, in combination, a plurality of cooperating pairs of electrically-energizable fieldestablishing means, each pair comprising spaced facing cores for producing a narrow concentrated heat-inducing magnetic field extending across the depth of the work-passage, each core of one pair of field-establishing means also being laterally spaced from a core on the same side of the work-passage which is a part of another pair of said field-establishing means, means for moving material so that separate parts of the material longitudinally pass through said magnetic fields in a predetermined direction, and rollers laterally between the cores on the same side of the work-passage, said field-establishing means carrying roller supporting bearings in facing upstanding sides thereof for supporting said rollers.

' GLENN E. STOLTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

